comparison of constexpr hashed string with assembly

hashstr.cpp

#include <iostream>

constexpr unsigned _hash_string_recursive(unsigned hash, const char* str)
{
    return ( !*str ? hash :
    _hash_string_recursive(((hash << 5) + hash) + *str, str + 1));
}

constexpr unsigned hash_string(const char* str)
{
    return ( !str ? 0 :
    _hash_string_recursive(5381, str));
}

class HashedString
{
public:
    inline explicit constexpr HashedString(const char* str);

    inline constexpr bool operator==(const HashedString& other) const;
    inline constexpr bool operator!=(const HashedString& other) const;
    inline constexpr bool operator<(const HashedString& other) const;

    unsigned hash;
};


constexpr HashedString::HashedString(const char* str):
hash(hash_string(str))
{
}

bool constexpr HashedString::operator==(const HashedString& other) const
{
    return hash == other.hash;
}

bool constexpr HashedString::operator!=(const HashedString& other) const
{
    return hash != other.hash;
}

bool constexpr HashedString::operator<(const HashedString& other) const
{
    return hash < other.hash;
}

static_assert(HashedString("foo") != HashedString("bar"), "compare different hashed string by key");
static_assert(HashedString("foo") == HashedString("foo"), "compare identical strings by key");
static_assert(HashedString("bar") < HashedString("foo"), "compare strings by key ordering");

int main()
{
	HashedString foo("foo");
	HashedString bar("bar");

	if (foo != HashedString("foo"))
	{
		std::cout << "foo" << std::endl;
	}
	else if (HashedString("foo") != bar)
	{
		std::cout << "bar" << std::endl;
	}
}

hashstr.s

	.file	"hashstr.cpp"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"foo"
.LC1:
	.string	"bar"
	.section	.text.startup,"ax",@progbits
	.p2align 4,,15
	.globl	main
	.type	main, @function
main:
.LFB1283:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	$5381, %eax
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	movl	$102, %ecx
	pushl	%ebx
	movl	$.LC0, %edx
	andl	$-16, %esp
	subl	$16, %esp
	.p2align 4,,7
	.p2align 3
.L2:
	movl	%eax, %ebx
	.cfi_offset 3, -12
	movsbl	%cl, %ecx
	sall	$5, %ebx
	addl	$1, %edx
	addl	%ebx, %ecx
	addl	%ecx, %eax
	movzbl	(%edx), %ecx
	testb	%cl, %cl
	jne	.L2
	cmpl	$193491849, %eax
	jne	.L9
	movl	$5381, %eax
	movl	$102, %ecx
	movl	$.LC0, %edx
	.p2align 4,,7
	.p2align 3
.L3:
	movl	%eax, %ebx
	movsbl	%cl, %ecx
	sall	$5, %ebx
	addl	$1, %edx
	addl	%ebx, %ecx
	addl	%ecx, %eax
	movzbl	(%edx), %ecx
	testb	%cl, %cl
	jne	.L3
	cmpl	$193487034, %eax
	je	.L4
	movl	$.LC1, 4(%esp)
	movl	$_ZSt4cout, (%esp)
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
	movl	%eax, (%esp)
	call	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_
.L4:
	xorl	%eax, %eax
	movl	-4(%ebp), %ebx
	leave
	.cfi_remember_state
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	.cfi_restore 3
	ret
.L9:
	.cfi_restore_state
	movl	$.LC0, 4(%esp)
	movl	$_ZSt4cout, (%esp)
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
	movl	%eax, (%esp)
	call	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_
	jmp	.L4
	.cfi_endproc
.LFE1283:
	.size	main, .-main
	.p2align 4,,15
	.type	_GLOBAL__sub_I_main, @function
_GLOBAL__sub_I_main:
.LFB1439:
	.cfi_startproc
	subl	$28, %esp
	.cfi_def_cfa_offset 32
	movl	$_ZStL8__ioinit, (%esp)
	call	_ZNSt8ios_base4InitC1Ev
	movl	$__dso_handle, 8(%esp)
	movl	$_ZStL8__ioinit, 4(%esp)
	movl	$_ZNSt8ios_base4InitD1Ev, (%esp)
	call	__cxa_atexit
	addl	$28, %esp
	.cfi_def_cfa_offset 4
	ret
	.cfi_endproc
.LFE1439:
	.size	_GLOBAL__sub_I_main, .-_GLOBAL__sub_I_main
	.section	.ctors,"aw",@progbits
	.align 4
	.long	_GLOBAL__sub_I_main
	.local	_ZStL8__ioinit
	.comm	_ZStL8__ioinit,1,1
	.weakref	_ZL20__gthrw_pthread_oncePiPFvvE,pthread_once
	.weakref	_ZL27__gthrw_pthread_getspecificj,pthread_getspecific
	.weakref	_ZL27__gthrw_pthread_setspecificjPKv,pthread_setspecific
	.weakref	_ZL22__gthrw_pthread_createPmPK14pthread_attr_tPFPvS3_ES3_,pthread_create
	.weakref	_ZL20__gthrw_pthread_joinmPPv,pthread_join
	.weakref	_ZL21__gthrw_pthread_equalmm,pthread_equal
	.weakref	_ZL20__gthrw_pthread_selfv,pthread_self
	.weakref	_ZL22__gthrw_pthread_detachm,pthread_detach
	.weakref	_ZL22__gthrw_pthread_cancelm,pthread_cancel
	.weakref	_ZL19__gthrw_sched_yieldv,sched_yield
	.weakref	_ZL26__gthrw_pthread_mutex_lockP15pthread_mutex_t,pthread_mutex_lock
	.weakref	_ZL29__gthrw_pthread_mutex_trylockP15pthread_mutex_t,pthread_mutex_trylock
	.weakref	_ZL31__gthrw_pthread_mutex_timedlockP15pthread_mutex_tPK8timespec,pthread_mutex_timedlock
	.weakref	_ZL28__gthrw_pthread_mutex_unlockP15pthread_mutex_t,pthread_mutex_unlock
	.weakref	_ZL26__gthrw_pthread_mutex_initP15pthread_mutex_tPK19pthread_mutexattr_t,pthread_mutex_init
	.weakref	_ZL29__gthrw_pthread_mutex_destroyP15pthread_mutex_t,pthread_mutex_destroy
	.weakref	_ZL30__gthrw_pthread_cond_broadcastP14pthread_cond_t,pthread_cond_broadcast
	.weakref	_ZL27__gthrw_pthread_cond_signalP14pthread_cond_t,pthread_cond_signal
	.weakref	_ZL25__gthrw_pthread_cond_waitP14pthread_cond_tP15pthread_mutex_t,pthread_cond_wait
	.weakref	_ZL30__gthrw_pthread_cond_timedwaitP14pthread_cond_tP15pthread_mutex_tPK8timespec,pthread_cond_timedwait
	.weakref	_ZL28__gthrw_pthread_cond_destroyP14pthread_cond_t,pthread_cond_destroy
	.weakref	_ZL26__gthrw_pthread_key_createPjPFvPvE,pthread_key_create
	.weakref	_ZL26__gthrw_pthread_key_deletej,pthread_key_delete
	.weakref	_ZL30__gthrw_pthread_mutexattr_initP19pthread_mutexattr_t,pthread_mutexattr_init
	.weakref	_ZL33__gthrw_pthread_mutexattr_settypeP19pthread_mutexattr_ti,pthread_mutexattr_settype
	.weakref	_ZL33__gthrw_pthread_mutexattr_destroyP19pthread_mutexattr_t,pthread_mutexattr_destroy
	.ident	"GCC: (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3"
	.section	.note.GNU-stack,"",@progbits

interest

lines of interest in hashstr.s:
17: why is the hash magic number being moved into a register if the hashing function is already computed at compile-time?
17-37: if I'm not mistaken, this is the algorithm for calculating the string. Why does this code need to be executed if the answer is known in the very next line 38 after?
38: this is the integer representing the hashed string of "foo"
55: this is the integer representing the hashed string of "bar"